Not Applicable.
The present invention pertains generally to the field of spectroscopy. More particularly, the present invention pertains to an apparatus that permits substantially simultaneous collection, and subsequent comparison, of one or more emissions from a plurality of radiation beams. The present invention is particularly, but not exclusively, useful for comparing spectral measurements from scattered emission beams from one or more known qualified substances and one or more unknown but qualified substances, having substantially similar characterizations.
Spectroscopy is a general term for the process of measuring energy or intensity as a function of wavelength in a beam of light or radiation using an instrument generally referred to as a spectroscope. Many conventional spectroscopes, and components comprising a spectroscope system, also referred to as an instrument, may include features and components such as a slit through which radiation may pass, a collimator for producing a parallel beam of radiation, one or more prisms or gratings for dispersing radiation through differing angles of deviation based on wavelength, and components for viewing dispersed radiation. Spectroscopy uses absorption, emission, or scattering of electromagnetic radiation by atoms, molecules or ions to qualitatively and quantitatively study physical properties and processes of substances.
Light or radiation that during operation of a spectroscope system is to be directed at one or more substances may be referred to as excitation radiation. A beam of excitation radiation from a source of excitation radiation may be referred to as an excitation beam. As indicated, a spectroscopy instrument may include a number of components for directing, redirecting, dispersing, and modifying an excitation beam, including, without limitation, mirrors, gratings, wave guides, filters, lenses and similar components. An excitation beam may be directed at and through one or more of such components before being directed at selected substances.
Redirection of a radiation beam following contact with a substance commonly is referred to as scattering of radiation. To the extent that atoms or molecules in a substance absorb all or a portion of a beam of radiation, rather than reflect the radiation of an excitation beam, a substance may become excited, and the energy level of the substance may be increased to a higher energy level. Radiation that passes through a substance may produce a small portion of light that is scattered in a variety of directions. Radiation that is scattered but continues to have the same wavelength as the excitation radiation that contacted the substance may have the same energy, a condition often referred to as Rayleigh or elastically scattered light. Alternatively, radiation that is scattered during a change of vibrational state in molecules may be scattered with a different energy, and such scattered light is called Raman scattered light.
As regards Raman scattered light, a wave associated with electromagnetic radiation may be described by (i) wavelength, the physical length of one complete oscillation, and by (ii) frequency of the wave, the number of oscillations per second that pass a point. If radiation is directed at a substance, the wavelength of the radiation may remain substantially unchanged in scattered radiation. Alternatively, if radiation is directed at a substance, the wavelength in the scattered radiation may acquire one or more different wavelengths. The energy differential between the original radiation, and the scattered radiation, may be referred to as a Raman shift. The Raman shift is significant because spectroscopic measurement of Raman scattered light seeks to measure the resulting wavelength of such scattered light.
Raman phenomena are used in conjunction with spectroscopy to qualitatively and quantitatively study physical properties and processes of a substance, including without limitation, identification of chemical characterizations including, but not limited to, properties, compositions, and structures. The phenomenon of Raman scattered light, therefore, is useful in spectroscopy applications for studying qualities and quantities of physical properties and processes of substances, including identification of chemical properties, compositions, and structure of a substance. Raman shift spectroscopic analytical techniques are, therefore, applied to qualitative and quantitative studies of matter. If radiation is used to scatter light from a substance, and scattered radiation data is measured, the scattered radiation may provide one or more spectral data, including but not limited to frequencies associated with the substance, as well as the intensities of those shifted frequencies. The frequencies may be used to identify, without limitation, the chemical composition of the substance.
Merely identifying the chemical properties, composition, structure and other characterizations of a substance, however, is only one objective of use of Raman technology. Another objective of using the Raman phenomena in connection with spectroscopy is to rapidly obtain a high quality characterization of molecular matter. Raman spectroscopy frequently is used because Raman technology has the advantage of being nondestructive of physical matter being characterized. In addition, Raman technology requires minimal sample preparation, and often may provide information about an analyte although the analyte may be but a minor ingredient in a complex mixture or admixture of physical matter.
Although the qualitative capabilities of Raman technology have been recognized, providing and enhancing quantitative capabilities have remained challenging. A number of factors contribute to the lack of quantitative capabilities of Raman technology. For example, a single beam of radiation generally is used to implement Raman technology in connection with substance analyses. Conventional Raman experimentation often uses a source of incident radiation substantially monochromatic, preferably providing a single frequency or wavelength. Acceptance by those skilled in the art that the source of the excitation beam should be substantially monochromatic and provide a single frequency or wavelength has led to use of a variety of laser light sources as a source of excitation radiation. However, if an excitation beam changes frequency, the Raman shift calibration may be disturbed; if an excitation beam changes intensity, the Raman magnitude may change. Quantitative analysis also is complicated because, without the existence of a reference beam of radiation for comparison, instrumentation variabilities may affect the spectral shape of a Raman spectral measurement. A number of components of an instrument may contribute individually and collectively to undesirable instrumentation variabilities that affect spectral data measured by the instrument. Spectroscopic measurements of Raman scattered light, therefore, seeking to measure wavelength or intensities, or both, of scattered light, may be affected by the instrument, or spectroscopic system, itself.
While efforts have been introduced to compensate for these problems associated with quantitative Raman measurements, what still is needed is an apparatus that is independent of instrumentation variabilities, and has the capability of directly comparing one or more known qualified substances or materials with one or more known unqualified substances or materials whose spectral data have been collected simultaneously or substantially simultaneously.
Use of Raman technology would be enhanced if those and related problems were solved. At least one advantage of the novel present invention is that it provides an apparatus for substantially simultaneous collection of one or more emissions from a plurality of radiation beams. Another advantage of the present invention is the capability of the apparatus and method of the invention to compare spectral data and measurements from different beams from not only one or more known qualified substances, but also from one or more known unqualified substances, and to ascertain the similarity, or lack of similarity, between or among those substances having identical or substantially identical characterizations. As will be apparent to one skilled in the art, such an apparatus and method of operating the apparatus will achieve the objective and advantage of permitting direct comparison of Raman spectra of an known unqualified substance with a known qualified substance because the spectral data and measurements are collected substantially simultaneously, before comparison one with the other. Use of the same instrument in which the beams and spectral data are generated has the further advantage of attenuating or eliminating the effect of instrumentation variabilities on the spectral data. The ability of the present invention to substantially simultaneously collect spectral data measurements from one or more substances having substantially similar or substantially identical characterizations has important advantages over instruments currently available for conducting quality assurance and quality control, particularly where the objective is to verify that a measurement from a substance is similar to a known measurement from another qualified substance. An apparatus for substantially simultaneous measurement of one or more emissions from a radiation beam has the additional advantage of eliminating the need for a pre-established sample reference library.
At least one other advantage of the present invention, therefore, is elimination of the need to correct spectral data collected in connection with the substances. The instrument, which, as indicated, is often a spectrometer or its analog, need not be stabilized. Indeed, while Raman principles and phenomena are useful in operation of the invention, none of the Raman characteristics is determinative of the use and usefulness of the present invention. Raman characteristics are useful but not essential because an object of the invention is to compare spectral data of substances having substantially similar or identical characterizations. A number of other Raman apparatus and methods seek to correct spectral data to a true, correct or corrected, and relatively absolute standard. The present invention, however, does not seek to correct the spectral data, but only to compare spectral data.
Because the user seeks merely to compare data associated with substantially similar or substantially identical substances, means for comparison, including, but not limited to computer software programs, electronic hardware, or other devices useful in comparing or rationing data from multiple channels of an instrument, may be (i) quite simple in formulation, (ii) readily reprogrammed for a range of varying substances by the user of the present invention, and (iii) developed as decision-making programs, including merely xe2x80x9cgo-no goxe2x80x9d or xe2x80x9cyes-noxe2x80x9d programs, or ratioing techniques for different information of the channels of the instrumentation components. Complicated or sophisticated algorithms or integral transforms used with Raman technology seeking to determine convolution functions, convolved spectra of substances being studied with the apparatus, or seeking to determine the standard Raman spectra of substances, are not required. The present invention, therefore, provides an inexpensive, simple, and cost-effective method and apparatus for comparing the spectral data of known unqualified substances with known qualified substances. While some Raman apparatus and methods provide for correction of instrumentation variabilities, the present invention does not require correction of instrumentation variabilities to achieve the advantages of the apparatus and method of the present invention.
Other presently available Raman apparatus and methods provide for simultaneously performing certain tasks during operation of the instrument. Simultaneity, however, of what is achieved by the present invention differs markedly from what may be achieved simultaneously by current apparatus. For example, at least one Raman instrument currently available simultaneously compensates Raman data for instrumentation variabilities. The present invention, however, as indicated, is not concerned with instrumentation variabilities. In addition, some currently available instruments provide for simultaneously interfacing radiation with a sample and a reference material, producing convolved spectra, and then adjusting the convolved spectra of the sample for the sole purpose of producing a standard Raman spectrum. That, too, is not an objective of the present invention. The present invention does not seek to determine standard Raman spectra, but to compare spectral data yielded from application of Raman technology. Raman radiation is used in connection with the present invention to assist in the determination of whether an known but unqualified substance is similar or identical to a known and qualified substance. Accordingly, the goal of the invention is not dependent on or affected by laser mode hops, calibration errors, thermal problems, and similar instrument variations.
Another salutary feature of the present invention is to reduce or eliminate sample preparation before operation of the apparatus and application of a method of use. The present invention presupposes that the substances to be compared share substantially similar or identical characterizations. Sample preparation, therefore, is irrelevant to the present invention.
Perhaps the most simplistic explanation of the advantages of the present invention is to consider the present invention""s application in connection with composition of a substance. A variety of Raman apparatus are responsive to the question, xe2x80x9cWhat is the composition of the sample?xe2x80x9d Users of the present invention are not concerned with the composition of a substance per se. Instead, users of the present invention are interested in the answer to the question, xe2x80x9cIs one substance the same as another substance?xe2x80x9d As previously stated, a capability of the present invention includes determining the similarity, or lack of similarity, between or among one or more known qualified substances, and one or more known unqualified substances, having substantially similar or substantially identical characterizations. An alternative way to explicate the novelty of the present invention is to identify the substances whose characterizations are being compared as qualified and unqualified. A qualified substance, as contemplated by the present invention, has been tested to confirm that the qualified substance comports with a standard set of characterizations. An unqualified substance has not been tested, but is presumed to have substantially similar or identical characterizations as the qualified substance. Unqualified substances, for example, may be produced during a production or manufacturing process using means to produce one or more substances similar to or identical with a qualified substance, but not yet proven to be substantially similar to or identical with a qualified substance until compared with one another using the present invention. Accordingly, the present invention has application in a variety of fields. The present invention would be useful, for example, not only in quality control processes, but also in any environment requiring comparison of characteristics, including medical diagnostics.
By using Raman analyses optics and the apparatus provided by the present invention, which may include a multi-spatial channel detector, the instrument has the capabilities of a double or multiple beam instrument. The result is an inexpensive instrument, and inexpensive method for using the instrument for comparing substances by optical and mechanical comparison. Using such an instrument, a user is able to quickly determine by direct comparison whether one substance, a sample, for example, is within the specifications prescribed for the substance in general. The present invention, therefore, would be appropriate for QA/QC applications where the goal is to compare one or more known unqualified substances with one or more known qualified substances and other materials. A limiting problem in current applications of Raman technology is the frequency axis instability of sequential Raman measurements. The present invention, however, eliminates the problem by making measurements of substances that are similar or identical, collecting the measurements substantially simultaneously, and using the same instrument for making the measurements. In other words, the substances being compared have substantially similar sampling geometry.
These advantages and other objects and features of such an apparatus and method for substantially simultaneous measurement of an emission will become apparent to those skilled in the art when read in conjunction with the accompanying following description, drawing figures, and appended claims.
An apparatus and method for substantially simultaneous measurement of a emissions, according to the present invention, includes a source of an excitation beam. The source of an excitation beam may include a laser. The apparatus for substantially simultaneous measurement of a emissions also includes means locatable in the path of the excitation beam for providing one or more daughter beams. In addition, the present invention includes means in the path of one or more daughter beams for directing a daughter beam at one or more substances. The substances at which a daughter beam may be directed include substances whose physical properties and characteristics are unknown, as well as substances whose physical properties and characteristics are known, and have substantially similar or substantially identical characterizations.
The apparatus of the present invention also includes means adjacent the one or more substances, and locatable in the path of the one or more daughter beams, for generating one or more emission beams. An emission beam from a substance may be a Raman beam, and may include Raleigh scattered radiation as well as fluorescence. A spectral analysis device also is provided in connection with the present invention. The spectral analysis device also may be a multiple channel imaging spectrograph connectable to the emission beam generating means for collecting substantially simultaneously spectral measurements from the one or more emission beams. The spectral analysis device may be connected to the emission beam generating means. The present invention advances Raman technology in a variety of ways, including providing an apparatus for substantially simultaneously collecting spectral measurements from one or more emission beams and comparing the spectral measurements of one or more known unqualified substances with one or more known qualified substances. Accordingly, the spectral analysis device provided with the present invention may be an imaging spectrograph, one having multiple channels. By substantially simultaneously collecting spectral measurements or spectral data from one or more emission beams with the same instrument components, and by using emission beam generating means that are substantially identical, a number of problems are overcome that presently reduce the effectiveness of some qualitative and quantitative analyses using some Raman instruments. The present invention minimizes or eliminates qualitative measurement problems by providing an apparatus, and method of operating the apparatus, that is independent of instrumentation variabilities, and has the capability of directly comparing one or more known unqualified substances with one or more known qualified substances whose spectral data have been collected simultaneously, or substantially simultaneously, with the same instrument. The spectral analysis device of the present invention, therefore, is capable of collecting substantially simultaneously spectral measurements from each of the emission beams by substantially simultaneously receiving emission beams for measurement. Problems associated with sequential measurements are eliminated. In addition, the device for generating emission beams are substantially identical in physical components, construction, and assembly. The present invention also includes means combinable with the spectral analysis device for comparing the spectral measurement from the emission beams using means well known in the art.
The advantages of the present invention are achieved by use of instrument structural components in a different manner than instruments currently are used in connection with Raman technology. The need to correct spectral data collected in connection with the substances is unnecessary. The instrument of the present invention need not be stabilized. None of the Raman characteristics such as wavelength and frequency is important because spectral data of substantially similar substances are compared. The present invention does not seek to correct spectral data, but only to compare spectral data. The present invention, however, does not require correction of instrumentation variabilities.
What is achieved simultaneously using the present invention differs significantly from what may be achieved simultaneously using other Raman instruments. For example, at least one Raman instrument currently available compensates for instrumentation variabilities. Comparisons between and among known and unknown substances is accomplished. This eliminates instrumentation variabilities as a concern. The present invention is not concerned with obtaining an absolute Raman spectrum. Raman radiation is used in connection with the present invention to assist in the determination of whether one an unknown but qualified substance is similar or identical to a known qualified substance. Accordingly, the goal of the invention is not dependent on or affected by laser mode hops, calibration errors, thermal problems, and similar instrument variations. A useful feature of the present invention is reduction or elimination of sample preparation before operation of the apparatus and application of a method of use because the substances to be compared share substantially similar or identical characterizations.
The foregoing has outlined broadly the more important features of the invention to better understand the detailed description which follows, and to better understand the contribution of the present invention to the art. Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in application to the details of construction, and to the arrangements of the components, provided in the following description or drawing figures. The invention is capable of other embodiments, and of being practiced and carried out in various ways. Also, the phraseology and terminology employed in this disclosure are for purpose of description, and should not be regarded as limiting.
As those skilled in the art will appreciate, the conception on which this disclosure is based may be used as a basis for designing other structures, cooperation of structure, methods, and systems for carrying out the purposes of the present invention. The claims, therefore, include such equivalent constructions. Further, the abstract associated with this disclosure is neither intended to define the invention, which is measured by the claims, nor intended to be limiting as to the scope of the invention.
The novel features of this invention, and the invention itself, both as to structure and operation, are best understood from the accompanying drawing, considered in connection with the accompanying description of the drawing, in which similar reference characters refer to similar parts, and in which: